1. Field of the Invention
The present invention is apparatus and a method for cutting or sawing a slab of stone or similar material.
2. The Prior Art
A substantial number of patents are concerned with apparatus for cutting slabs of stone, concrete or the like. These include: British Patent No. 1,058,958 of Wholton et al.; U.S. Pat. Nos. 2,736,311 of Coates; 5,442,984 of Tate; 3,207,016 of Huff, 4,998,775 of Hollifield; 5,398,458 of Henriksen et al.; and 2,619,081 of Johnson.
In these patents, the slab of stone remains fixed and the cutter is mounted on a carriage that is moved along a set of parallel rails that are spaced above the slab. In some instances, such as Wholton et al., Huff, and Tate, the rails are mounted on a table-like structure, while in other instances the rails are part of a large and heavy installation.
In order to provide an open space to accommodate the slab and to permit free passage of the cutting tool, it is common practice to support the rails at their ends only. The desirability of being able to make lengthy cuts is well recognized. As a result, the rails in the prior art devices were lengthy compared to the cross sectional size of the rails.
The difficulty of making these extended rails rigid can be readily appreciated. Pure sagging of the rails in a vertical direction was tolerable since it affected mainly the depth of the cut. However, several other factors were at work.
First, the carriage that was moved along the rails was not balanced, with the result that the carriage applied more weight to one of the rails than to the other. The more heavily loaded rail sagged more, thereby causing the top of the cutting blade to tilt laterally toward the more heavily loaded side.
A second source of inaccuracy was caused by the manner in which the carriage was pushed along the rails. Ordinarily, the carriage was pushed by the user, and no special precautions were taken to assure that the applied force, which often included a downward component, was equally distributed between the two rails. Depending on the location of the handgrip relative to the rails, it was not unusual for one of the rails to be loaded more heavily than the other, again resulting in a tilting of the cutter blade.
The typical reaction of prior art designers to these causes of inaccuracy was to make the rails and their supporting structures less flexible. In most instances this resulted in a much heavier structure, which therefore was much less portable. It was generally thought that lightweight apparatus could not produce accurate cuts, and if accurate cuts were to be achieved, a large, heavy, and therefore non-portable machine was required.
Thus, conventional design philosophy, starting with the assumption that the rails must be spaced above the workpiece, led to the conclusion that accurate cutting could only be achieved with large, heavy, fixed installations and that lightweight portable equipment could not produce cuts of satisfactory accuracy.
The present inventor has devised a totally different design approach that runs counter to the conventional design philosophy and that permits remarkable accuracy to be achieved with lightweight portable equipment.